The present invention relates broadly to body cavity piercing devices used in surgery to provide access to internal cavities through small puncture sites rather than large incisions. More particularly, the present invention is directed to such a body cavity piercing device, known as a trocar, having a multi-portion obturator, or multiple obturator portions.
A standard trocar is typically a pointed rod, usually formed from metal, which is designed to be contained within a blunt-tipped sleeve known as a cannula. The tip of the trocar is typically needle-like with a beveled piercing tip having sharp edges.
A tissue puncture is manually conducted with the combination trocar and cannula, and then the trocar is removed from the cannula The cannula is left in place to provide an access conduit to the internal body cavity. According to one of two typical trocar designs, a retractable sleeve is positioned around the trocar, with the sleeve being biased such that it slides back on contact with the outer walls of the body cavity covering to expose the tip of the trocar during insertion, but is advanced forwardly to cover the sharp point of the trocar once the internal cavity has been breached.
Another style of trocar is similar in design to a Verress needle, which consists of a sharp tubular needle with an internal blunt obturator provided with a passageway for fluid, the internal obturator being spring biased so that it is forced into the body of the needle during piercing or puncture. Throughout the present application, the terms piercing and puncturing are used interchangeably. The tubular needle itself pierces the tissue, while the obturator blocks the interior of the needle to prevent tissue from entering into the needle. This type of trocar, which is also used in combination with a cannula, has a sharp tubular member or sleeve containing a retractable obturator, with the obturator being spring biased so that the tissue will push it some small distance into the sleeve during the puncture or piercing event. When the tip of the trocar reaches the internal cavity, which is usually inflated with a gas in a procedure known as insufflation, to provide an enlarged cavity, the biasing spring pushes the obturator forward past the sharp tip of the sleeve to prevent accidental puncturing or cutting of internal organs.
It is sometimes difficult for a surgeon to ascertain when the internal cavity wall has been breached by the trocar. Typically, the only indication provided by a standard trocar is a reduction in the amount of resistance felt by the surgeon, with a vibration or sound caused by the forward movement of the spring biased sleeve or obturator once the trocar has entered the internal cavity. Various devices have been developed to provide a more positive indication of when the cavity wall has been breached. These devices typically utilize visual or audible signals.
Other problems with conventional trocar assemblies include the capture of tissue intermediate the obturator and the piercing sleeve wall when the obturator is retracted or pushed back by the body cavity wall. Since the tip is beveled, the initial piercing and cutting is performed by the forwardmost extent of the blade formed on the beveled edge of the sleeve. Once the initial opening is formed, further insertion of the trocar generally forms an aperture in the body cavity wall absent any meaningful cutting action from the remainder of the beveled edge of the trocar sleeve. Therefore, the cut at the trailing edge of the beveled tip may not be as smoothly formed as the initial cut and retraction of the obturator can capture tissue intermediate the obturator and the sleeve.